Headlamp for automotive vehicles

ABSTRACT

A vehicle headlamp comprises a reflector and a headlamp glass constructed to produce a so-called full beam lobe when a light source is located in a predetermined position in relation to the reflector. The invention is characterized in that the light source (11) is constructed to transmit both a large proportion of visible light and a large proportion of ultraviolet light, and in that a filter (19; 22; 23) is located in the beam path of the headlamp and is effective in filtering that part of the light emitted by the light source (11) which gives rise to a light lobe corresponding to the difference between a so-called full beam lobe and a so-called dipped beam lobe. The headlamp is further characterized in that the filter (19; 22; 23) is constructed firstly to filter light so that substantially no light within the visible light spectrum will be transmitted through the filter, and secondly to transmit ultraviolet light.

BACKGROUND OF THE INVENTION

The present invention relates to a headlamp for automotive vehicles.

Automotive vehicles, such as cars, are normally provided with mainheadlights which are constructed to emit a full beam image, or high beamimage, and a dipped beam image, or low beam image. For at least 15years, vehicles have been fitted with halogen headlamps in order toincrease the light yield.

It is a generally known problem that while the full beam of a vehicleheadlamp will illuminate the surroundings well ahead of the vehicle indarkness, the beam will also dazzle the occupants of any oncomingvehicle. On the other hand, whereas the dipped beam will not have thesame dazzling effect on oncoming vehicles, it does not illuminate thesurroundings ahead of the vehicle to a satisfactory extent. Normally,however, the extent of illumination afforded by a dipped beam isadequate enough to enable the driver to see the road sufficiently wellto drive the vehicle.

However, the ability to discern roadside objects, such as road signs andother fixtures, or pedestrians etc., is greatly impaired when driving ondipped headlights rather than on full beam.

Since the illuminating lobe of a dipped headlight with appreciable lightintensity, is not higher than about 0.5 to 1 meter above the roadsurface, the light reflected from the road sign or other roadside objectis often too weak to be discerned readily by the occupants of thevehicle. The distances at which safety reflectors carried by pedestrianscan be observed safely are also much shorter when the vehicle is ondipped headlights than when driven on full beam.

The light yield could be increased still further, by replacing theconventional halogen headlamps with gas discharge lamps.

One drawback with gas discharge lamps, however, is that their ignitiontime is of such long duration as to render it impossible to switchrapidly between full beam and dipped beam.

A progressively increasing desire in this respect is one of fitting toautomotive vehicles lamps capable of emitting ultraviolet light. Thislight causes a large number of different colours to fluoresce to greaterand lesser extents. In recent times it has become more and more usual toutilize so-called day-glow inks on signs etc., i.e. inks which whenirradiated with ultraviolet light (UV) will transmit visible light.Roadside objects are today painted with such day-glow inks and paints.Furthermore, some emergency vehicles have broad strips painted thereonin day-glow colours. Light-coloured clothing will also fluoresce wellwhen illuminated with ultraviolet light.

If it were possible for a vehicle to transmit ultraviolet light, itwould render the painting of road signs, roadside demarcation posts,etc. with a fully or partially day-glow paint more viable than is nowthe case, from a road safety aspect.

However, as beforementioned, the use of gas discharge lamps which emit ahigh proportion of ultraviolet light is seriously encumbered by the longignition times of such lamps.

SUMMARY OF THE INVENTION

The present invention offers a solution which will fulfill the aforesaiddesideratum, where the dependency of the long ignition times of gasdischarge lamps has been eliminated.

Accordingly, this invention relates to a vehicle headlamp that comprisesa reflector and a headlamp glass which are constructed to produce aso-called full beam lobe when a light source is located in apredetermined position in relation to the reflector, said headlamp beingcharacterized in that the light source is constructed to emit both alarge proportion of visible light and a large proportion of ultravioletlight; in that located in the beam path of the lamp is a filter which isintended to filter that part of the light emitted by the light sourcewhich will give rise to a light lobe corresponding to the differencebetween a so-called full beam lobe and a so-called dipped beam lobe; andin that the filter is constructed firstly to filter light so thatsubstantially no light within the visible light spectrum will betransmitted through the filter and secondly to transmit ultravioletlight.

The invention will now be described in more detail with reference toexemplifying embodiments thereof illustrated in the accompanyingdrawings, in which

BRIEF DESCRIPTION OF THE DRAWING

FIGS. 1 and 2 illustrate schematically light lobes produced by thedipped and full beams respectively of a vehicle; FIG. 3 is a schematiccross-section of a headlamp and illustrates three different embodimentsof the invention; and

FIG. 4 illustrates a headlamp glass seen from the right of FIG. 3,according to a first inventive embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 illustrate a road surface 1 and a car 2 which travels inthe direction of the arrow shown when seen in the horizontal plane, thelobe of a low beam or dipped beam may have the appearance indicated byphantom line 3, whereas the lobe of a full beam or high beam may havethe appearance indicated by phantom line 4. FIG. 2 illustratescorresponding lobes 3, 4 seen in the vertical plane. As illustrated, anormal dipped beam has a relatively short and broad lobe, the verticalextension of which does not extend to more than 0.5-1 meter above theroad surface. A full beam has a narrower and longer lobe, the verticalextension of which is significantly more than one meter above the roadsurface.

The inventive headlamp is constructed and fitted to the vehicle so thatvisible light and ultraviolet light are emitted in the schematicallyillustrated lobe 3, corresponding to a dipped beam lobe, and so thatultraviolet light, substantially in the absence of visible light, isemitted in a light lobe corresponding to the difference between the fullbeam lobe 4 and the dipped beam lobe 3.

FIG. 3 is a cross-sectional view of a headlamp 10 constructed inaccordance with the invention.

The light source 11 of the headlamp 10 is a gas discharge lamp,preferably a mercury vapour discharge lamp, which will produce both alarge proportion of visible light and a large proportion of ultravioletlight. Other known types of electrical discharge lamps are conceivable.

The ultraviolet light will preferably have a wave length in afluorescence activating range of 360-370 nanometers.

The headlamp reflector 12 is configured so that together with theheadlamp glass it will produce a full beam image when the light source11 is located in a predetermined position relative to the reflector. Thereference 13 identifies those light rays which impinge on the roadsurface at a closer distance to the vehicle, i.e. light rays whichtogether with approximately horizontal light rays 14,15, 16 result in atypical dipped beam lobe 3. The references 17,18 identify those lightrays which typically produce the light lobe which distinguishes the fullbeam lobe from the dipped beam lobe, i.e. the light contained by thelobe 4 minus the light contained by the lobe 3.

In accordance with the invention, there is positioned in the beam pathof the headlamp, a filter which is effective in filtering that part ofthe light emitted by the light source which gives rise to a light lobecorresponding to the difference between the so-called full beam lobe andthe so-called dipped beam lobe. The filter is constructed to filter thelight so that firstly substantially no light within the visible lightspectrum will be transmitted through the filter and secondly ultravioletis transmitted.

According to a first embodiment of the invention, the filter comprisesan integral part 19 of the headlamp glass 20. The remaining part 21 ofthe headlamp glass consists of conventional headlamp glass.

The filter 19 may comprise any filter suitable for the purpose intended,although a filter made of Woods glass is preferred.

Since a mercury vapour discharge lamp is used, the light yield is veryhigh. Despite producing a high proportion of ultraviolet light, theintensity of the visible light emitted will correspond to the intensityproduced by a conventional halogen lamp.

It has been said in the aforegoing that the visible light is filteredout by the filter. A greater or lesser part of the visible light will betransmitted through the filter, however, depending on the constrictionof the filter.

According to the invention, however, substantially no light which lieswithin the visible light spectrum is transmitted through the filter.

By "substantially no light which lies within the visible light spectrum"is mean there and in the following claims that the intensity of anyvisible light that may be present will lack all significance in respectof the application in question For example, when the invention isapplied in automobiles this definition implies that any visible lightpresent will not have a troublesome effect on the driver of an oncomingvehicle.

According to a second embodiment of the invention, the filter is placedin the beam path between the light source 11 and the headlamp glass 20.

FIG. 3 illustrates two different variants according to said secondembodiment. According to a first variant a filter 22 is placed betweenthe light source 11 and the reflector 12, this filter 22 being shown inphantom lines in FIG. 3.

According to a second variant, a filter 23 is placed between thereflector 12 and the inner surface of the headlamp glass 20, this filter23 being shown in phantom lines in FIG. 3.

Thus, a headlamp which is constructed in accordance with the inventionwill transmit a dipped beam lobe of visible and ultraviolet lighttogether with ultraviolet light in a lobe which correspondssubstantially to the difference between a full beam lobe and a dippedbeam lobe.

As beforementioned, the ultraviolet light activates day-glow paints, andconsequently objects which are painted with such paints or whichincorporate day-glow inks or colouring substances will be illuminatedwhen located within the light lobe of the ultraviolet light. The driverof a vehicle will observe such objects despite said objects beinglocated in an area not irradiated by visible light. Thus, in the case ofthe FIG. 1 example, the lights of the vehicle 1 will not dazzle thedriver of the vehicle 5 while objects 6, 7 which are located outside thelight lobe of the dipped beams of the vehicle 1 will be illuminated forthe driver of said vehicle. Naturally, the ultraviolet light in thedipped beam lobe will assist the driver in noticing objects within thedipped beam lobe more readily. These objects 6, 7 may, for instance, beroad signs or pedestrians wearing clothes which carry day-glow colours.

As mentioned in the introduction, a multiple of different objects aretoday painted in day-glow colours, so that they can be more readilynoticed in daylight. The use of day-glow paints or colours can beexpected to increase.

In addition hereto a large number of materials used in clothes areday-glowing in the sense that when irradiated with ultraviolet lightthey transmit light of a longer wave length, i.e. visible light. Themajority of synthetic fibre materials, for instance, are day-glowing.

It will be obvious that the inventive headlamp can be switched oncontinuously while the vehicle is driven in darkness. In other words,the headlamp need not be dimmed.

When the invention is applied in automobiles, however, the automobilewill preferably be fitted with a conventional halogen headlamp whichproduces a full beam lobe. Naturally, this additional headlamp must bedimmed when two vehicles meet.

Despite dimming the further headlamp, however, the headlamp constructedin accordance with the present invention will enable the driver of avehicle to discern much more readily objects that are located within thearea illuminated by the additional headlamp.

It will be understood that the filter can be made from a material otherthan Woods glass, such as any material capable of filtering out visiblelight but transmitting ultraviolet light. It will also be understoodthat the configuration of the filter and the positioning thereof can bedifferent to that illustrated in FIG. 3.

Consequently, the present invention shall be not be considered to belimited to the afore described embodiments, since variations andmodifications can be made within the scope of the following claims.

I claim:
 1. A vehicle headlamp comprising: in combination, a reflector,a headlamp glass and a light source, said combination being structurallyarranged so that the beam path from the light source produces a fullbeam lobe with said light source located in a predetermined position inrelation to said reflector, and wherein said light source (11) emitsboth a large proportion of visible light and a large proportion ofultraviolet light; and a filter (19; 22; 23) is disposed in thecombination and fixed in the beam path of the headlamp in a locationwherein that part of the light emitted by the light source (11) whichgives rise to a light beam lobe, corresponding to the difference betweena full beam lobe and a dipped beam lobe, passes through said filter; andsaid filter (19; 22; 23) being constructed of material which will filterlight so that substantially no light within the visible light spectrumis transmitted through the filter, and so that ultraviolet light willpass through said filter.
 2. A headlamp according to claim 1, whereinsaid filter (19) forms an integral part of the headlamp glass (20) ofsaid headlamp.
 3. A headlamp according to claim 1, wherein said filter(22; 23) is located in at least a part of the beam path between thelight source (11) and through the headlamp glass.
 4. A headlampaccording to claim 1, wherein said light source (11) comprises a gasdischarge lamp.
 5. A headlamp according to claim 4, wherein said lightsource (11) is constructed to emit a large proportion of light withinthe wave length range of 360 to 370 nanometers, and a large proportionof light within the visible light spectrum.
 6. A headlamp according toclaim 3, wherein said filter is located between the light source and thereflector in the path of said part of the light emitted by the lightsource.
 7. A headlamp according to claim 3, wherein aid filter islocated between the reflector and the headlamp glass in the path of saidpart of the light emitted by the light source.
 8. A headlamp accordingto claim 4, wherein said light source comprises a mercury vapourdischarge lamp.